MANILA (Reuters) - Philippine senators abruptly ended a hearing on Monday into allegations by a retired policeman that a "death squad" operated under President Rodrigo Duterte when he was mayor of Davao City, citing no proof that it even existed.

Arturo Lascanas admitted to lying in October during another Senate inquiry into alleged extrajudicial killings by a hit squad linked to Duterte, but said he did so for his family's safety and because police had warned him to "deny everything".

He said on Monday he had personally killed 300 people, about 200 as a member of a "Davao death squad" of which Duterte had full knowledge.

But few fresh claims emerged in Monday's proceedings and the senators, several of whom are Duterte loyalists, challenged his credibility and demanded proof.

"We don't see any point of pursuing the investigation," Senator Panfilo Lacson, head of the Senate panel, told reporters.

"There's no independent evidence other than what he had already testified on."

Lascanas broke down when he told his story to reporters two weeks ago and is the second person to testify before lawmakers on Duterte's alleged links to a clandestine hit squad.

The hearing was much anticipated after Lascanas had written in the final line of his sworn affidavit that his allegations were just "the tip of a bloody iceberg".

But little more came during Monday's inquiry. Lascanas cited one time when Duterte had personally instructed him to kill and said the death squad's instructions were usually relayed by senior policemen, or Duterte's bodyguard.

Lascanas said he shot dead nine of 11 arrested Chinese drug suspects on orders that came indirectly from Duterte. He also alleged Duterte's son and current Davao vice mayor, Paulo Duterte, had links to the drug trade.

The president's allies say the testimony is part of a broader plot to discredit him. His chief lawyer, Salvadore Panelo, said Duterte's alleged involvement in extrajudicial killings was "a fabrication".

TORMENTED BY KILLINGS

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Lascanas had in October denied the death squad existed. On Monday he said he was tormented by what he had done and wanted the truth to set him free. He said he spoke out because of "the fear of God".

"I wanted to clear my conscience," he added

Duterte denies ordering summary executions, either as president or during his 22 years as Davao mayor. His top police commander, Ronald dela Rosa, a former Davao police chief, calls the death squad "fiction" created by the media.

Human rights groups documented about 1,400 suspicious killings in Davao while Duterte was mayor and critics say the war on drugs he unleashed as president has the same hallmarks.

More than 8,000 people have been killed since Duterte took office eight months ago, mostly drug users killed by mysterious gunmen in incidents authorities attribute to vigilantes, gang members silencing informants, or unrelated murders.

Police reject activists' allegations that they are behind most killings and say they are responsible for 2,555 of the deaths, when suspects had resisted arrest.

On Monday, dela Rosa announced the re-launch of police anti-narcotics operations after a month-long suspension of police involvement in the campaign.